The Patek N° 17 ref3940 Perpetual Calendar, that was sold by Beyer, Zurich (Switzerland) 1985 for the 225th Anniversary of the oldest Patek-AD in the Zurich, Bahnhofstr, is something extraordinary and special. It comes up for auction by Artcurial in Basel in one week -- *klikk -- and a final price north of CHF300'000 would not be a big surprise.
Chronometrie Beyer is a foundational pillar in the Swiss watch-industry and they not only sold amazing and outstanding watches but also marked the most important pieces of each era with their double-signature print. They did so for the important Patek ref3940 in 1985 (big photo, source Artcurial) and they did so with a highest quality feminine IWC almost 30y before (1957, bottom-left).
They also marked the important innovation by Eterna "EternaMatic" on a Golfer automatic-pocketwatch almost 20y before (1966, middle-right) and just 10y before the proudly doublesigned Patek ref3940 they sold a high quality IWC Savonette (1975, top-right).
Just a few years before the Patek Calendar wristwatch was sold by Beyer they proudly marked a similar impressive IWC Calendar pocketwatch with their now-popular doublesignature "BEYER" (~1980, bottom-right).